Effect of UV-Ozone Treatment on Poly(dimethylsiloxane) Membranes: Surface Characterization and Gas Separation Performance

Abstract

A thin SiO(x) selective surface layer was formed on a series of cross-linked poly(dimethylsiloxane) (PDMS) membranes by exposure to ultraviolet light at room temperature in the presence of ozone. The conversion of the cross-linked polysiloxane to SiO(x) was monitored by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX) microanalysis, contact angle analysis, and atomic force microscopy (AFM). The conversion of the cross-linked polysiloxane to SiO(x) increased with UV-ozone exposure time and cross-linking agent content, and the surface possesses highest conversion. The formation of a SiO(x) layer increased surface roughness, but it decreased water contact angle. Gas permeation measurements on the UV-ozone exposure PDMS membranes documented interesting gas separation properties: the O(2) permeability of the cross-linked PDMS membrane before UV-ozone exposure was 777 barrer, and the O(2)/N(2) selectivity was 1.9; after UV-ozone exposure, the permeability decreased to 127 barrer while the selectivity increased to 5.4. The free volume depth profile of the SiO(x) layer was investigated by novel slow positron beam. The results show that free volume size increased with the depth, yet the degree of siloxane conversion to SiO(x) does not affect the amount of free volume.

Control of pore structure and characterization of plasma-polymerized SiOCH films deposited from octamethylcyclotetrasiloxane (OMCTS)

“…The details of the apparatus (Yanaco Gas Permeability Analyzer, model GTR-10) used for the gas permeability measurement at isothermal conditions at 35 • C (±0.5 • C) were given in our previous study [19]. The gas permeability was calculated with the following equation:…”

Base-treated polydimethylsiloxane surfaces as enhanced triboelectric nanogenerators

“…Figure 3a shows ATR FT-IR spectra of fresh, UVO (1 h), UVO (2 h), and NaOH (2 h) +UVO (1 h)-treated PDMS surfaces. One of the most noticeable changes is the Si-OH vibrational bands located around 850 and 3300 cm À 1 [21,22]. The band near 3300 cm À 1 is almost absent in fresh PDMS and is easily observable in UVO-treated PDMS.…”

“…Hence, Raman scattering measurements with a large penetration depth could not detect such changes in the Si-OH band ( Figure S6 in Supporting information). The other noticeable changes is the Si-CH 3 vibrational bands near 1250 and 2960 cm À 1 [21,22]. These bands are reduced following UVO and NaOH treatments.…”

OMCVD Gold Nanoparticles Covalently Attached to Polystyrene for Biosensing Applications

“…The UVO treatment relies upon the combined effects of UV light and ozone, produced in situ from a gas-phase photodissociation of molecular oxygen. The system contains a mercury vapour lamp which emits UV light of major wavelengths 184.9 nm and 253.7 nm [71]. When the atmospheric molecular oxygen (O2) is exposed to 184.9 nm UV light, oxygen absorbs the ultraviolet rays to form ozone (O3) and atomic oxygen (O * ) as given in Eq.…”